The present invention relates to a seat testing body for vibration measurements on seats, having simulated buttocks which point downwards in the testing position and can be placed on a seat cushion of a seat to be tested, and a simulated back which is connected therewith and, in the testing position, can be placed against the backrest cushion of a seat to be tested. The seat testing body, with respect to its weight and its mass distribution, corresponds approximately to the sitting weight and the mass distribution of a person of an average weight.
When seats, particularly vehicle seats are developed, a high sitting comfort is important because, particularly when vehicle seats are involved, the occupants and mainly the driver may have to stay in the seat for many hours while not being able to move very much. Among other things, questions concerning a good vibration performance of the seat are also significant here. In the course of the development of a seat, different seat and cushioning constructions are produced as testing specimens, and these must be objectively and reproducibly compared with one another with respect to various testing and evaluation criteria so that then the best testing specimen can be selected. Not only new testing specimens of a current seat development stage but also various test seats of other provenances, such as seats of earlier generations, used seats or seats from outside development or manufacturing facilities of any pairing are compared with one another.
For vibration tests, the seat with a testing person sitting therein or with a seat testing body placed thereon is excited to carry out vertical vibrations and the response vibrations of the testing body or of the testing person are measured. During the vibration measurements, flat cushion-shaped acceleration sensors are placed in the contact zone of the buttocks with the surface of the seat cushion and this vibration is measured as the response vibration. The obtained response vibrations are entered in a diagram as a spectral distribution of the vibration amplitudes relative to the corresponding excitation amplitude. The so-called transmission curves--starting with a very slow quasi-static excitation--are determined into the range of approximately 30 Hz. Typically, these transmission curves start at a value of 1.0 and then have a clear resonance point in the range of approximately 5 Hz. Then they, as a rule, fall clearly below the value of 1 and fall slightly, in a range of the seat damping, with an increasing excitation frequency.
DE 41 03 374 C1 describes a seat testing body which consists of several vertically vibratory, damped spring/mass systems for the simulation of the vertical vibration tendency of body members and body regions. The weight and the mass distribution of the spring/mass systems correspond approximately to the sitting weight of a person of an average weight. Before the vibration test of a seat with the known seat testing body, this body is placed loosely on the seat cushion of the seat and is placed against the backrest cushion.
Comparative measurements have been carried out by the assignee of this application with the known seat testing bodies, on one hand, and human testing persons, on the other hand, on various seats. The comparison of the measurements demonstrates that only in the range of the resonance step-up do the measurements result in correct information and even there only in information which is tendentiously correct. The resonance step-up determined by the assignee with the known seat testing body quantitatively did not correspond to the values measured with human testing persons. In the assignee's experience, the measuring results of the known seat testing body are even less comparable in the range of the seat damping. That is, the transmission curve determined with the seat testing body rises above approximately 7 Hz and reaches even excess values toward the end of the measuring range, which are partially clearly above the resonance step-up, whereas the testing person measurements showed a drop of the transmission values to below 0.5. A comparison between a well damping seat and a less well damping seat shows that the known seat testing body furnishes useful measuring values not even tendentiously. This comparison demonstrates that, at least according to the assignee's experiences, the known seat testing body supplies information which can be compared only to a very limited degree with the information supplied with testing person measurements and cannot replace this type of measurements. Vibration tests of seats could therefore only be carried out by using human testing persons. This naturally requires high expenditures with respect to time and personnel and can also hardly be expected.
The seat testing body described in DE 41 03 374 C1 is based on a uniaxial impedance model of the human being according to DIN 45 676. The known seat testing body disadvantagely supplies values only in the vertical position and during uniaxial vibrations in the vertical direction. It fails to stimulate a realistic seat position and real vibrations which are always three-dimensional.